On 03/06/2012 03:28 AM, Ted Ts'o wrote:
On Tue, Mar 06, 2012 at 01:40:05AM +0100, Bernd Schubert wrote:
Yeah, you are right, we also should check for 64-bit EOF. But
wouldn't be something like this be better?
/* check for hash collision */
if(is_32bit_api() ) {
if (hash == (EXT4_HTREE_EOF_32BIT<< 1))
hash = (EXT4_HTREE_EOF_32BIT - 1)<< 1;
} else {
if (hash == (EXT4_HTREE_EOF_64BIT<< 1))
hash = (EXT4_HTREE_EOF_64BIT - 1)<< 1;
}
Actually, neither change is needed, now that I look at things more
closely. hash is a __u32, so it could never been
EXT4_HTREE_EOF_64BIT. But given that we won't let major hash become
larger than 0xfffffffc, that means the largest possible position value
is 0x7ffffffeffffffff. So using an EOF value of 0x0x7fffffffffffffff
will work fine.
Ah, I looked after 1 a.m., seems that was too late for me to notice.
The bigger problem that I found when I looked more closely at the
patch is that the patch uses f_flags in places where f_mode needs to
be used:
static inline loff_t hash2pos(struct file *filp, __u32 major, __u32 minor)
{
if ((filp->f_flags& FMODE_32BITHASH) ||
^^^^^^^
(!(filp->f_flags& FMODE_64BITHASH)&& is_32bit_api()))
^^^^^^^
return major>> 1;
else
return ((__u64)(major>> 1)<< 32) | (__u64)minor;
}
static inline __u32 pos2maj_hash(struct file *filp, loff_t pos)
{
if ((filp->f_flags& FMODE_32BITHASH) ||
^^^^^^
(!(filp->f_mode& FMODE_64BITHASH)&& is_32bit_api()))
^^^^^^
return (pos<< 1)& 0xffffffff;
else
return ((pos>> 32)<< 1)& 0xffffffff;
}
Which makes me wonder how much this has been tested?
Arg, my bad, I introduced this issue when I converted from f_flags to
f_mode, seems I forgot all of those above :(
Hrm, I thought I had tested sufficiently, but obviously I did not :(
Here's the test tool.
http://www.pci.uni-heidelberg.de/tc/usr/bernd/downloads/test_seekdir/
While quickly looking, I think it only affects NFSv2, which I think I
indeed didn't test. I only run tests for 32 bit and 64-bit user space
and NFSv3. But yes, NFSv2 is an important test too. Not sure if I will
find time for that today.
Will send an updated version later on.
Thanks for your review,
Bernd
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